1. Field of the Invention
The present invention relates to a radio transmitter for use in apparatus such as radio communication apparatus, remote control apparatus, wireless LAN apparatus, and key-less entry apparatus.
2. Description of the Related Art
FIG. 4 shows a circuit for a conventional radio transmitter, which includes a Colpitts oscillator. The collector of a transistor Tr is connected to ground through a series circuit including bias resistors R1 and R2 as well as to the power voltage V.sub.CC. The base of the transistor is connected to ground through a series circuit including capacitors C1 and C2, and through a SAW resonator "re", the base being connected to a connecting point where the resistors R1 and R2 and the SAW resonator "re" are connected. The emitter of the transistor is connected to a connecting point where the capacitors C1 and C2 are connected, and to ground through a resistor R3. In addition, the collector of the transistor Tr is connected to ground through a series circuit including a capacitor C3, an antenna ANT, and a capacitor C4. The antenna ANT emits a radio wave which is received from the collector side of the transistor Tr.
Since the antenna is disposed outside the oscillation loop in the conventional radio transmitter, oscillating power is supplied to both the oscillation loop and the antenna. Thus, the efficiency of power transmission from the oscillation loop to the antenna is relatively low.